This invention relates to thermoplastic graft polymers with improved weatherability and processability.
Weatherability, as used in describing this invention, refers to the ability of the graft polymer to retain desirable physical properties such as impact strength, on exposure to environmental conditions such as high temperature, ultraviolet light, high humidity, rain and other elements generally included in discussions of weatherability.
Weatherable graft polymers, which are described in U.S. Pat. Nos. 4,585,832, 4,766,175 and 4,877,826, use acrylate and EPDM rubbers over butadiene type rubbers which tend to break down in the presence of sunlight. The weatherable polymers are prepared by graft polymerizing a vinyl aromatic monomer such as styrene, an ethylenically unsaturated monomer such as acrylonitrile and optionally additional monomers such as methyl methacrylate and the like onto an acrylate rubber or an ethylene-propylene-diene rubber (EPDM). The graft copolymers are blended with a rigid polymer such as a styrene acrylonitrile copolymer to form weatherable graft polymer compositions.
It is an object of this invention to provide a weatherable graft polymer composition having improved processability and weather resistance.